The present invention relates to a breath-actuated inhaler for delivery of medicament by inhalation.
Inhalers are commonly used for delivery of a wide range of medicaments. A known type of inhaler holds a canister which is compressible to deliver a dose of medicament through a mouthpiece. It is known to provide the inhaler with an actuation mechanism for compressing the canister. The actuation mechanism may be breath-actuated to actuate the canister in response to inhalation at the mouthpiece. Typically, a breath-actuated inhaler might include a loading mechanism for loading a resilient biassing element which is arranged when loaded to bias compression of the canister, and a triggering mechanism arranged to hold the resilient biassing element against compression and to release the resilient loading element upon inhalation.
Known canisters comprise a body having a protruding valve stem and an internal metering chamber which receives a dose of medicament from the body where the medicament is stored under pressure. Compression of the valve stem into the body causes the medicament in the metering chamber to be delivered out of the valve stem as a dose. The valve stem is biassed outwardly to reset the canister after compression to deliver the next dose of medicament. However, if the compression of the canister is released to allow reset of the valve stem too early, then a full dose is not properly delivered. The present invention is intended to ensure proper delivery of a full dose.
According to the present invention, there is provided an inhaler for delivery of medicament from a canister which is compressible to deliver a dose of medicament, the inhaler comprising:
a housing for holding a canister, the housing having a mouthpiece for inhalation of a dose of medicament delivered by the canister;
a breath-actuated actuation mechanism for compressing a canister held in the housing in response to inhalation at the mouthpiece;
the actuation mechanism including a locking mechanism arranged to lock the canister in a compressed state and being responsive to the inhalation at the mouthpiece to release the canister when the level of inhalation at the mouthpiece falls below a predetermined threshold.
The locking mechanism ensures that reset of the canister does not occur immediately but is delayed until the level of inhalation at the mouthpiece falls below the predetermined threshold. Accordingly, a full dose is properly delivered from the canister. Typically it is necessary for the user to take a deep breath to ensure proper inhalation of the medicament so the delay for reset of the canister is sufficiently long.
Preferably, the locking mechanism includes a vane responsive to airflow created by inhalation at the mouthpiece and arranged to release the locking mechanism when the level of inhalation at the mouthpiece falls below said predetermined threshold. A vane provides simple but reliable detection of the level of inhalation falling below the predetermined threshold. Furthermore, the vane may also be arranged to trigger the actuation mechanism upon inhalation at the mouthpiece so that the vane has a joint purpose. This simplifies the actuation mechanism of the inhaler and reduces the complexity of its airflow paths. Alternatively, an electronic sensor could be used to control the locking mechanism making it responsive to inhalation.
Preferably, the vane is disposed in a duct extending from the mouthpiece. By providing the vane in a duct, it is possible to control the level of the predetermined threshold by appropriately designing the duct and the vane.
Desirably, the vane is a flap extending across the duct. This improves the reliability of operation, because it ensures that all the inhalation at the mouthpiece acts on the vane.
Desirably, the end of the duct opposite from the mouthpiece opens into the interior of the housing. This ensures that the duct is protected from the outside thereby assisting in preventing the vane from being interfered with and accidentally operated or else jammed, for example by insertion of an object or finger. Preferably the vane is disposed at the end of the duct opposite from the mouthpiece. This increases the distance of the vane from the mouthpiece, preventing interference with the operation of the vane.
The present invention may be applied to an inhaler having an actuation mechanism which comprises a loading mechanism for loading a resilient biassing element which is arranged, when loaded, to bias compression of the canister, and a triggering mechanism arranged to hold the resilient biassing element against compression and triggerable to release the resilient biassing element.
Desirably, the loading mechanism drives a loading member coupled to the resilient loading element to load the resilient loading element, and the locking mechanism is arranged to hold the loading element in a loaded state, thereby locking the canister in its compressed state after release of the triggering mechanism. Such a structure prevents the locking element from interfering with the operation of the actuation mechanism to deliver a dose.
Preferably, the locking mechanism includes a moveable catch held in a locking position where the catch locks the canister in a compressed state upon inhalation at the mouthpiece and released when the level of inhalation at the mouthpiece falls below said predetermined threshold.
Desirably, the locking mechanism further comprises an intermediate member coupled to the catch through a resilient biassing element arranged to bias the catch towards the locking position, the loading mechanism engaging the intermediate member upon inhalation at the mouthpiece to load the resilient biassing member, thereby to hold the catch in said locking position, and releasing the intermediate member when the level of inhalation falls below said predetermined threshold to unload the resilient biassing element, thereby to release the catch. The provision of the resilient biassing element coupling the intermediate member to the catch allows the catch to be forced open upon loading of the actuation mechanism.